Variable‐ratio Versus Variable‐interval Schedules: Response Rate, Resistance to Change, and Preference

Abstract

Two experiments asked whether resistance to change depended on variable-ratio as opposed to variable-interval contingencies of reinforcement and the different response rates they establish. In Experiment 1, pigeons were trained on multiple random-ratio random-interval schedules with equated reinforcer rates. Baseline response rates were disrupted by intercomponent food, extinction, and prefeeding. Resistance to change relative to baseline was greater in the interval component, and the difference was correlated with the extent to which baseline response rates were higher in the ratio component. In Experiment 2, pigeons were trained on multiple variable-ratio variable-interval schedules in one half of each session and on concurrent chains in the other half in which the terminal links corresponded to the multiple-schedule components. The schedules were varied over six conditions, including two with equated reinforcer rates. In concurrent chains, preference strongly overmatched the ratio of obtained reinforcer rates. In multiple schedules, relative resistance to response-independent food during intercomponent intervals, extinction, and intercomponent food plus extinction depended on the ratio of obtained reinforcer rates but was less sensitive than was preference. When reinforcer rates were similar, both preference and relative resistance were greater for the variable-interval schedule, and the differences were correlated with the extent to which baseline response rates were higher on the variable-ratio schedule, confirming the results of Experiment 1. These results demonstrate that resistance to change and preference depend in part on response rate as well as obtained reinforcer rate, and challenge the independence of resistance to change and preference with respect to response rate proposed by behavioral momentum theory.

Effects of Behavioral History on Resistance to Change

“…Both Lattal (1989) and Nevin, Grace, Holland, and McLean (2001) found, with reinforcement rate equated, greater resistance to change for lower, as opposed to higher, response rates. A crucial difference between this experiment and the studies of Lattal and Nevin et al is that the present resistance tests occurred while responding was maintained by identical schedules.…”

Dynamical Concurrent Schedules

“…The probability of a reinforcer in each bin was set to vary from 0.067 to 0.002 across the 5-min trial (equivalent to a shift from a VI 15-s to a VI 480-s schedule). In this random interval schedule, the first peck in each bin was probabilistically reinforced (Millenson, 1963;Nevin, Grace, Holland, & McLean, 2001). The first peck in the first bin on one key was followed by food presentation with a probability of 0.067.…”

Training reinforcement rates, resistance to extinction, and the role of context in reinstatement

“…These findings are generally robust and have been observed in a variety of animal species, ranging from fish to humans, as well as several response types and reinforcer manipulations (Ahearn, Clark, Gardenier, Chung, & Dube, 2003;Cohen, 1996;Grimes & Shull, 2001;Harper, 1999;Igaki & Sakagami, 2004;Mace et al, 1990;Shahan & Burke, 2004). However, exceptions to the finding that resistance to disruption is independent from baseline response rate responding have been observed (e.g., Lattal, 1989;Nevin, Grace, Holland, & McLean, 2001;Podlesnik, JimenezGomez, Ward, & Shahan, 2006).…”